Approximation of the exponential function

Using Frama-C/Jessie
with the strict-IEEE float model, we specify a
bound on the total error expected from that function. An assertion in
the code is inserted to express the mathematical error, that is
without taking rounding in account.

This is proved by a combination of automated provers (SMT solvers and
Gappa) and the Coq proof assistant.

The following screenshot shows that SMT solvers and Gappa verify all the
verification conditions except the mathematical method error. The latter
is verified inside Coq using the interval tactic, shown
on the second screenshot below.